WEST CHESTER, Ohio (AP) -- His campaign rocked anew, a feisty Herman Cain claimed a "groundswell of positive support" from backers on Wednesday and accused critics of trying to derail his White House bid as he worked to stem the fallout from allegations of a 13-year extramarital affair.

"They're attacking my character, my reputation and my name in order to try to bring me down," a feisty Cain told a friendly crowd without naming his critics. "But, you see, I don't believe that America is going to let that happen."

Questions about the campaign's viability hovered over Cain's one-day bus tour through Ohio.

It came a day after the candidate told staff he was reassessing his campaign after Ginger White, an Atlanta businesswoman, alleged in media interviews that she and Cain had a long-running sexual affair.

"We are reassessing as we speak. Reassessment means reevaluation," Cain told reporters Wednesday after his well-received speech to roughly 150 people in a hotel meeting room. He gave no indication to the audience that he was considering abandoning his bid despite telling staff that he would make a decision in the next few days about whether to continue it.

Cain received a standing ovation after he spoke about what a "Cain administration" would do. And he said that while some people predicted that the room would be empty, "I don't see any empty seats."

"It's been a groundswell of positive support," Cain insisted to reporters later, even as some backers in early voting states of Iowa and New Hampshire who had stuck by him after decade-old allegations of sexual harassment surfaced several weeks ago now indicated they were abandoning him.

Cain's latest turmoil comes just five weeks before the first votes are cast in the state-by-state march to the nomination. The earlier sexual harassment accusations that have taken a toll on both his standing in polls and, supporters say, his fundraising. Prominent conservatives who rushed to his defense earlier this month were all but silent when White stepped forward on Monday to accuse Cain of a consensual sexual relationship that ended this year before he became a White House candidate.

The candidate has denied the affair, and in a letter addressed to "patriots and supporters," called her allegations "completely false" and labeled her "troubled."

White steadfastly stood by her assertion in an interview Wednesday on ABC's "Good Morning America" and said she was "disappointed" by Cain's characterization of her. She called her relationship with Cain "a very casual affair" that lasted more than a dozen years.

"I'm not here to say anything negative about Mr. Cain," White said, although White added that she didn't think he should be president.

She elaborated on her claims, saying she took several trips with Cain, including a flight to Las Vegas to see a Mike Tyson-Evander Holyfield boxing match. She also said she had "consistently" received gifts and money from Cain over the past two and a half years, but said it was "not sex for cash."

Following Monday's developments, some Cain supporters have started to defect.

New Hampshire state Rep. William Panek endorsed Cain at a news conference earlier this year. But he changed his mind Tuesday after seeing reports that White showed evidence that she had traded 61 text messages and cellphone calls with the candidate. Panek has endorsed former House Speaker Newt Gingrich in the upcoming primary.

"I felt like we were being lied to," he said. "I'm putting my name in New Hampshire as a state rep behind him, and I just didn't like the way it was being played out."

In Iowa, Cain's campaign has lost some precinct-level supporters following the new allegations, according to Steve Grubbs, Cain's Iowa chairman. Cain was in Iowa for a day last week to film a new ad, but aides say that spending to air it was on hold pending the fundraising in the days to come.

Still, some are sticking by him.

Florida state Rep. Scott Plakon, one of four chairmen for Cain's Florida campaign, said he wanted to see more evidence.

"If it is true that he didn't do this, I think he should fight and kick and scratch and win," Plakon said.

But if Cain did have the affair, Plakon said, "that would be very problematic," he said. "There's the affair itself and then there's the truthful factor. He's been so outspoken in these denials."

White's revelation was the latest setback for a candidate who has been under scrutiny in the past month, since it was revealed that the National Restaurant Association paid settlements to two women who claimed Cain sexually harassed them while he was president of the organization. A third woman told The Associated Press that Cain made inappropriate sexual advanced toward her but that she didn't file a complaint. A fourth woman also stepped forward to accuse Cain of groping her in a car in 1997.

Cain has denied wrongdoing in all cases.

Outwardly on Wednesday, the candidate tried to project an image of a campaign focused on winning - and not damage control. He planned to continue his bus tour in Dayton and Columbus before heading to New Hampshire later in the day.

On Tuesday, Cain delivered a national security speech to nearly 1,000 people at conservative Hillsdale College in Michigan. He didn't address White's allegations; he also avoided speaking to reporters and stuck to his plan to present his foreign policy vision, one in which the U.S. would stand by friendly nations such as Israel, quit giving money to countries he considered enemies and spend more on defense.

Earlier that day, he acknowledged the "firestorm" that White sparked, and he acknowledged he was assessing whether her claims are too much for his candidacy to go forward.

"If a decision is made, different than to plow ahead, you all will be the first to know," Cain said during the call, according to a transcript from the National Review, which listened in.

In connection with the White allegation, Cain said: "With this latest one, we have to do an assessment as to whether or not this is going to create too much of a cloud, in some people's minds, as to whether or not they would be able to support us going forth."